Organic electroluminescence (EL) devices have been recently developed. Organic EL devices generate almost no heat, and thus a power consumption thereof is lower than that of cathode ray tubes. In addition, since the organic EL devices are self-emissive devices, they have advantages, such as a wider viewing angle and the like, compared to liquid crystal displays (LCDs), and thus, future growth of the organic EL devices is being expected.
A conventional organic EL device basically has a sandwich structure in which an anode layer, a light emitting layer, and a cathode layer are stacked on a glass substrate. In order to bring out light from the light emitting layer to outside, a transparent electrode formed of indium tin oxide (ITO) is used as the anode layer on the glass substrate. The conventional organic EL device is generally fabricated by forming the light emitting layer and the cathode layer sequentially on the ITO layer (the anode layer) which is formed in advance on the glass substrate.
An apparatus for forming a light emitting layer of such an organic EL device is disclosed in Japanese Patent Laid-open Publication No. 2004-79904 (hereinafter, referred to as reference 1).
In a process of forming the light emitting layer of the organic EL device, a pressure in a processing chamber is reduced to a predetermined level. Because, when the light emitting layer of the organic EL device is formed as above, a vaporized layer forming material at a high temperature of about 200° C. to 500° C. is supplied from a deposition head to be deposited on a surface of a substrate and the heat of the vaporized layer forming material may increase temperatures of components such as various sensors disposed in the processing chamber due to air convection in the processing chamber, thereby degrading characteristics of the components or damaging the components, if the light emitting layer is deposited in an atmosphere. Therefore, when the light emitting layer of the organic EL device is formed, an internal pressure in the processing chamber is reduced to a predetermined level so that the heat of the vaporized material does not propagate to other components (vacuum heat insulation).
However, since a substrate transfer mechanism is placed in the processing chamber, a contaminant may be generated from the transfer mechanism and negatively affects the layer forming operation, when the internal pressure in the processing chamber is reduced. More specifically, the transfer mechanism generally includes a linear guide for guiding a stage which supports the substrate along a linear path, a driving motor for moving the stage, and a metal roller. Thus, when the internal pressure of the processing chamber is reduced, grease used as a lubricant in the linear guide may vaporize, and then, the vaporized grease may be mixed as a contaminant into the light emitting layer of the organic EL device.
Also, in this case, since the linear guide moves without the grease, particles are generated due to friction in the linear guide, and thus, the processing chamber cannot be maintained clean. Recently, a thin film formed of MoS2 and so on as a solid lubricant, has been deposited on a surface of a metal ball using a sputtering method to ensure lubrication, and thus omission of grease has been attempted. However, even in this case, particles may be generated in the processing chamber, and moreover, the solid lubricant does not have a long lifespan, and thus, it is difficult to maintain properties of the solid lubricant.
In another case, the linear guide that may cause a contamination of the processing chamber may be accommodated in a bellows or the like, however, it is difficult to dispose the bellows in the processing chamber of which internal pressure is reduced, and the bellows may make the overall structure of the processing chamber complex. Therefore, increase of fabrication costs and an enlargement of an installation space may occur. In addition, byproducts attached to the bellows may drop in the processing chamber due to the contraction of the bellows, thereby staining the processing chamber. In addition, since a vacuum bellows has a large surface area, a desired degree of vacuum cannot accomplish due to a discharged gas from the surface of the bellows.
Therefore, the present invention provides a mechanism for transferring the substrate without causing contamination by using a simple structure in the processing chamber of which internal pressure is reduced.